That depends on what you mean when you use the word "possible". There are many things in the universe that have a mathematical non-zero probability, but which have such a small probability of ever happening that no reasonable person would ever use the word "possible" to describe them.
If it happened (it hasn't), then the only way we'd be able to know for certain would be if BOTH individuals each spent separate outputs that had the same pubKey hash, but provided two different public keys for their transaction. This would be a pretty straight-forward search for someone to write software to perform on the blockchain, but I'm not going to waste my time writing it.
If only one of the individuals spent the outputs, then there'd only be one public key, and no way for us to know.